US9877042B1 - Position encoder sample timing system - Google Patents

Position encoder sample timing system Download PDF

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Publication number
US9877042B1
US9877042B1 US15/606,449 US201715606449A US9877042B1 US 9877042 B1 US9877042 B1 US 9877042B1 US 201715606449 A US201715606449 A US 201715606449A US 9877042 B1 US9877042 B1 US 9877042B1
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encoder
time
current
trigger
sample period
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Bjorn Erik Bertil Jansson
Andrew Michael Patzwald
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Mitutoyo Corp
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Mitutoyo Corp
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Priority to JP2018098682A priority patent/JP7041002B2/ja
Priority to CN201810517159.9A priority patent/CN109374022B/zh
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/50—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding
    • H04N19/503—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using predictive coding involving temporal prediction
    • H04N19/51—Motion estimation or motion compensation
    • H04N19/513—Processing of motion vectors
    • H04N19/517—Processing of motion vectors by encoding
    • H04N19/52—Processing of motion vectors by encoding by predictive encoding
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
    • G01D5/22—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature differentially influencing two coils
    • G01D5/225—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature differentially influencing two coils by influencing the mutual induction between the two coils
    • G01D5/2258—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature differentially influencing two coils by influencing the mutual induction between the two coils by a movable ferromagnetic element, e.g. core
    • G01D5/2266—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature differentially influencing two coils by influencing the mutual induction between the two coils by a movable ferromagnetic element, e.g. core specially adapted circuits therefor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/12—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means
    • G01D5/14—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage
    • G01D5/20—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature
    • G01D5/22—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable using electric or magnetic means influencing the magnitude of a current or voltage by varying inductance, e.g. by a movable armature differentially influencing two coils
    • G01D5/2291—Linear or rotary variable differential transformers (LVDTs/RVDTs) having a single primary coil and two secondary coils
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03M—CODING; DECODING; CODE CONVERSION IN GENERAL
    • H03M1/00—Analogue/digital conversion; Digital/analogue conversion
    • H03M1/12—Analogue/digital converters
    • H03M1/22—Analogue/digital converters pattern-reading type

Definitions

  • This disclosure relates generally to position encoders, and more particularly to systems and methods for determining the timing of position sampling in position encoders.
  • an encoder may comprise a transducer with a readhead and a scale.
  • the readhead may comprise a transducer element and some transducer electronics.
  • the transducer outputs signals which vary as a function of the position of the readhead relative to the scale along a measuring axis.
  • the transducer electronics outputs the signals to a signal processor or processes the signals internally before outputting modified signals indicative of the position of the readhead relative to the scale. It is also common for an encoder system to include interface electronics separate from the readhead, and to interpolate or otherwise processes the transducer signals in the interface electronics before outputting modified signals indicative of the position of the readhead relative to the scale to an external host.
  • Some position encoder systems communicate with an external host using a request and response process. This process may include three steps: the external host sends a request for a position measurement (e.g., a position trigger signal); the encoder samples the output of the position transducer; and the encoder responds by transmitting position information.
  • a position measurement e.g., a position trigger signal
  • the encoder samples the output of the position transducer
  • the encoder responds by transmitting position information.
  • a position encoder system including a position encoder that is configured to be utilized for outputting encoder position data corresponding to encoder positions and an encoder position timing subsystem.
  • the position encoder system receives position trigger signals from a host motion control system.
  • a method for operating the position encoder system initially determines predictable times when position trigger signals are expected to be received from the host motion control system.
  • a pre-trigger lead time is determined that is a fraction of the duration of a defined encoder position sample period during which the position encoder performs operations to acquire encoder position data associated with a current encoder position (e.g., by sampling a position transducer of the position encoder).
  • the encoder position timing subsystem is operated to initiate a current instance of the encoder position sample period at the pre-trigger lead time before a next predictable time of the position trigger signal.
  • An associated current instance of the encoder position data is determined as corresponding to the current instance of the encoder position sample period.
  • a current position trigger signal is received from the host motion control system, wherein the average effective sample time of the current instance of the encoder position sample period coincides with the actual timing of the current position trigger signal within an allowed tolerance window.
  • the position encoder is operated to output the current instance of the encoder position data at a time associated with the current position trigger signal, such that the host motion control system associates the current instance of the encoder position data with the current position trigger signal. It will be appreciated that such techniques reduce the overall timing between when the position trigger signal is received from the host motion control system and when the position encoder responds with position data.
  • FIG. 1 is a block diagram of a position encoder system as coupled to a host motion control system
  • FIG. 2 is a block diagram of multiple position encoder systems as coupled to a host motion control system
  • FIG. 3 is a block diagram of a readhead and interface electronics of a position encoder
  • FIG. 4 is a timing diagram illustrating signals in a position encoder system in accordance with a first exemplary implementation
  • FIG. 5 is a timing diagram illustrating signals in a position encoder system in accordance with a second exemplary implementation.
  • FIG. 6 is a flow diagram illustrating one exemplary implementation of a routine for operating a position encoder system.
  • FIG. 1 is a block diagram of a positioning system 100 including a position encoder system 105 that is coupled to a host motion control system 130 .
  • the position encoder system 105 includes a position encoder 110 , which may be any type of encoder, such as a linear position encoder intended for use by servo controllers in applications such as pick-and-place machines, fluid dispensing machines, etc., and interface electronics 118 .
  • the position encoder 110 includes a scale 112 , a readhead 114 , and a cable 117 .
  • an encoder position timing subsystem 119 may be included in the interface electronics 118 .
  • an encoder position timing subsystem 119 may be a separate component that is included within or outside of the position encoder system 105 , as will be described in more detail below with respect to FIG. 2 .
  • the host motion control system 130 e.g., in the form of a servo controller, etc. communicates via a cable 120 with the position encoder system 105 to send position requests (e.g., position trigger signals) and to receive position information.
  • the host motion control system 130 sends commands (e.g., position trigger signals) over the cable 120 to the interface electronics 118 .
  • the interface electronics 118 may communicate via the cable 117 with the readhead 114 .
  • the interface electronics 118 trigger position acquisition operations in the readhead 114 .
  • the encoder position timing subsystem may provide a pre-trigger signal that triggers the position acquisition ahead of when the position trigger signal is received from the host motion control system.
  • the readhead 114 collects and/or provides signals that are dependent on the position of the scale 112 relative to a readhead transducer element 115 , digitizes the signals using transducer electronics 116 , and sends the signals via the cable 117 to the interface electronics 118 .
  • the interface electronics 118 may compute a position from the signals, and may send the position information to the host motion control system via the cable 120 .
  • all or part of the interface electronics 118 may be configured as a plug-in card and/or embedded software routines or the like, and included in the host motion control system 130 , and in such cases the cable 120 may be eliminated.
  • the readhead 114 may receive power from a separate connection (not shown), and the transducer electronics 116 and the interface electronics 118 may be connected by any now known or later developed wireless communication methods.
  • the interface electronics 118 may be included in or adjacent to the readhead 114 , and the cable 117 may be eliminated or replaced by any other appropriate type of connection.
  • the transducer that is utilized in the readhead 114 may be an inductive transducer.
  • inductive transducers Various examples of some exemplary embodiments of inductive transducers are described in U.S. Pat. Nos. 6,011,389, and 6,005,387, which are commonly assigned and hereby incorporated herein by reference in their entireties.
  • there may be various types of factors for such transducers e.g., inductance and/or impedance of the transducer element, including transmitter and/or receiver coils, etc.
  • a “transmitter setup” time e.g., during which certain components take time to charge up as an initial part of a sampling process, etc.
  • the scale 112 may be a linear absolute position scale that includes a fine track and one or more coarser tracks.
  • absolute position encoders with scales utilizing a fine track in combination with two coarser tracks are described in U.S. Pat. Nos. 7,608,813 and 8,309,906, which are commonly assigned and hereby incorporated herein by reference in their entireties.
  • the position encoder system 105 and host motion control system 130 may operate in a request and response format. In prior systems this process has included three steps. First, the host motion control system 130 would send a request for position (e.g., a position trigger signal). In various implementations, the request for position may be issued at a fixed time interval (e.g., according to a known frequency). Once the position request was received, the position encoder system 105 would operate to sample the output of the transducer electronics 116 . Finally, the position encoder system 105 would respond by transmitting position information to the host motion control system 130 .
  • a request for position e.g., a position trigger signal
  • the request for position may be issued at a fixed time interval (e.g., according to a known frequency).
  • the position encoder system 105 would operate to sample the output of the transducer electronics 116 .
  • the position encoder system 105 would respond by transmitting position information to the host motion control system 130 .
  • the timing between the request for position information and the response may be an important factor.
  • certain newer interfaces may have specifications that require a position encoder to respond to a position request from a host motion control system within a relatively short time frame.
  • a position encoder may be required to respond with position data within 10 microseconds of when a position request is received from a host motion control system. While such response times may, in some instances, be achieved with high speed data converters, such components may be relatively expensive and/or difficult to design into an integrated circuit.
  • a pre-trigger lead time is determined that is a fraction of a duration of a defined encoder position sample period.
  • a current instance of the encoder position sample period is then initiated by a pre-trigger signal that is provided at the pre-trigger lead time before a next predictable time of a position trigger signal (e.g., as occurring at regular intervals).
  • a current position trigger signal is then received (e.g., near the middle of the current instance of the encoder position sample period) from the host motion control system.
  • the average effective sample time of the current instance of the encoder position sample period coincides with the actual timing of the current position trigger signal within an allowed tolerance window.
  • a position output can be produced more quickly relative to when the position request is received.
  • an additional benefit of such techniques is that a centroid of the position sample may more closely coincide with the actual timing of the position request.
  • the numerical position computed from the sample may, during constant speed operation, approximately match the actual encoder position at the time of the sample centroid. As a result, the numerical position that is returned from the request may at least approximately coincide with the timing of the position request.
  • FIG. 2 is a block diagram emphasizing certain aspects of a positioning system 200 including three position encoder systems 205 A- 205 C that are coupled to a host motion control system 230 . Similar references numbers 2 XX in FIGS. 2 and 1XX in FIG. 1 , may refer to similar elements unless otherwise indicated by context or description.
  • Each of the position encoder systems 205 A- 205 C includes a respective position encoder 210 A- 210 C, a respective encoder position timing subsystem 219 A- 219 C and a respective interface circuit 281 A- 281 C (e.g., as may be included in the interface electronics of position encoder systems 205 A- 205 C, described above with reference to FIG. 1 ).
  • each of the respective encoder position timing subsystems 219 A- 219 C is coupled between a respective position encoder 210 A- 210 C and the host motion control system 230 .
  • each of the encoder position timing subsystems 219 A- 219 C may be included in the respective position encoders 210 A- 210 C (e.g., within readhead electronics of the position encoders, as previously outlined in the description related to FIG. 1 ).
  • each of the encoder position timing subsystems 219 A- 219 C receives position trigger signals from the host motion control system 230 .
  • the encoder position timing subsystems 219 A- 219 C may determine and utilize a pre-trigger lead time for each of the position encoders 210 A- 210 C. More specifically, for each of the position encoders 210 A- 210 C, the respective encoder position timing subsystem 219 A- 219 C may operate to provide a pre-trigger signal to initiate a current instance of the respective encoder position sample period at the pre-trigger lead time before a next predictable time of the position trigger signal from the host motion control system 230 .
  • the position encoders 210 A- 210 C may each have the same or different encoder position sample periods, for which the pre-trigger lead times that are determined by the encoder position timing subsystems 219 A- 219 C may also be different. For example, if the position encoder 210 A has a defined encoder position sample period that is longer than a defined encoder position sample period of the position encoder 210 B, the associated pre-trigger lead time that is determined and utilized by the encoder position timing subsystem 219 A may be longer than the pre-trigger lead time that is determined and utilized by the encoder position timing subsystem 219 B.
  • the host motion control system 230 outputs position trigger signals PTS on a signal line 211 which is coupled as an input to each of the respective encoder position timing subsystems 219 A- 219 C.
  • each of the encoder position timing subsystems 219 A- 219 C outputs at a determined pre-trigger lead time a respective pre-trigger signal PRT-A to PRT-C on respective signal lines 212 A- 212 C to the respective position encoders 210 A- 210 C.
  • the position encoder timing subsystems 219 A- 219 C are operated to output the pre-trigger signals PRT-A to PRT-C and thus initiate the current instances of the encoder position sample periods at the respective pre-trigger lead times before a next predictable time of a position trigger signal PTS from the host motion control system 230 .
  • PRT-A the pre-trigger signals
  • PRT-C the pre-trigger signal
  • the respective encoder position data EPD-A to EPD-C is output to interface circuits 281 A- 281 C (e.g., serial interface circuits), which provides corresponding position data formatted on respective signal lines 213 A- 213 C that are coupled to the host motion control system 230 .
  • interface circuits 281 A- 281 C e.g., serial interface circuits
  • each of the position encoders 210 A- 210 C may be utilized to determine a position along a different axis of movement (e.g., along x, y and z axes of movement) of the positioning system 200 .
  • the position encoder 210 A may be utilized for determining a position along an x-axis
  • the position encoder 210 B may be utilized for determining a position along a y-axis
  • the position encoder 210 C may be utilized for a determining position along a z-axis.
  • one or more of the position encoders may be utilized for determining other types of position data (e.g., rotary, movement of components in different physical locations of the positioning system 200 , etc.).
  • FIG. 3 is a block diagram 300 showing certain aspects of a position encoder system 305 .
  • a readhead 314 of a position encoder 310 may refer to similar elements or functions, and may be understood by analogy unless otherwise indicated by context or description.
  • the interface electronics 318 may be included in the readhead 314 (e.g., on a single printed circuit board).
  • the readhead 314 includes a transducer element 315 and transducer electronics 316 .
  • the transducer may be an inductive transducer, which is illustrated schematically in FIG. 3 .
  • the transducer element 315 includes a receiver coils portion 350 and a transmitter coils portion 355 .
  • the receiver coils portion 350 includes receiver coils 351 A, 351 B and 351 C
  • the transmitter coils portion 355 includes transmitter coils 356 A, 356 B and 356 C.
  • the coupling between the transmitter coils and the receiver coils is “position modulated” by the scale 312 , which is configured such that the coupling modulation depends on the relative position between the scale 312 and the transducer element 315 , according to known methods.
  • the transducer electronics 316 inputs position modulated signals sensed by the receiver coil portions 350 .
  • the transducer electronics 316 includes a multiplexer 361 , amplifiers 363 A- 363 C, analog-to-digital converters 364 A- 364 C, a position signal processor 367 , and a transmitter driver/controller 370 .
  • the outputs of the receiver coils 351 A- 351 C are coupled through the multiplexer 361 to the amplifiers 363 A- 363 C, respectively.
  • the outputs of the amplifiers 363 A- 363 C are coupled to the analog-to-digital converters 364 A- 364 C, respectively.
  • the outputs of the analog-to-digital converters 364 A- 364 C are coupled to the position signal processor 367 .
  • the outlined components may operate according to known principles (e.g., as disclosed in the incorporated references) and/or as disclosed further below with respect to FIGS. 4 and 5 , to determine the absolute position of the position encoder according to the signals from the receiver coils 351 A- 351 C.
  • the interface electronics 318 may include serial interface circuits 381 (e.g., comprising an RS-485 interface), a command parser 382 , an encoder position timing subsystem 319 , and a clock generator 384 .
  • the interface electronics 318 may further include various other components not shown (e.g., power supply components, regulators, etc.) as desired or necessary, according to known principles.
  • the serial interface circuits 381 may receive the output from the position signal processor 367 and provide encoder position data formatted for outputting to a host motion control system 330 on a signal line(s) 313 . Power and/or other signals may be provided between the host motion control system 330 and the position encoder system 305 on line(s) 311 .
  • the clock generator 384 may provide a clock signal to the transducer electronics 316 .
  • various components and/or functions of the interface electronics 318 may be provided in a field programmable gate array, if desired.
  • FIG. 4 is a timing diagram 400 illustrating timelines 410 - 470 for various signals in a position encoder system in accordance with a first exemplary implementation.
  • a position request timeline 410 illustrates position trigger signals 412 and 414 (e.g., as received from a host motion control system), and corresponding pre-trigger signals 411 and 413 (e.g., as generated by an encoder position timing subsystem), as will be described in more detail below.
  • a sample scale A timeline 420 illustrates encoder position sample periods 421 and 425
  • a sample scale B timeline 450 illustrates an encoder position sample period 451
  • a sample scale C timeline 460 illustrates an encoder position sample period 461 .
  • each of the encoder position sample periods 421 , 425 , 451 and 461 correspond to a sampling of a respective scale track A, B or C (e.g., of the scale 112 of FIG. 1 ), wherein the scale track A corresponds to a fine scale track, and the scale tracks B and C correspond to coarser scale tracks.
  • a calculate fine position timeline 430 illustrates a fine position calculation period 431
  • an update coarse position timeline 470 illustrates coarse position update periods 471 and 472 .
  • the calculating and updating of the respective positions is performed after the end of each of the respective encoder position sampling periods 421 , 451 , 425 and 461 .
  • a serial response timeline 440 illustrates data transmission periods 442 and 445 .
  • each of the data transmission periods 442 and 445 correspond to the position encoder outputting a current instance of the encoder position data (e.g., as calculated and updated, etc.) to the host motion control system at a timing that is associated with a corresponding current position trigger signal 412 or 414 that was previously received from the host motion control system as part of a position request. More specific details regarding the operations of the position encoder system during each of the timelines 410 - 470 will be described in more detail below.
  • the pre-trigger signal 411 is generated (e.g., as provided by an encoder position timing subsystem) and at a time T 3 , the current position trigger signal 412 is received (e.g., from the host motion control system).
  • the pre-trigger signal 411 initiates the current instance of the encoder position sample period 421 , which begins at the time T 1 and ends at a time T 5 .
  • the encoder position sample period 421 corresponds to a sampling of a scale track A (e.g., a fine scale track of the scale 112 of FIG. 1 ).
  • the current instance of the encoder position sample period 421 includes a transmitter setup period 422 from the time T 1 to a time T 2 (e.g., for charging up the transmitter coils 356 A- 356 C of the transducer element 315 of FIG. 3 ), and an effective sample period 423 from the time T 2 to the time T 5 .
  • the effective sample period 423 has an average effective sample time 424 that corresponds to a time T 3 , which coincides with the actual timing of a current position trigger signal 412 within an allowed tolerance window ATW. In the particular example of FIG. 4 , the average effective sample time 424 and the actual timing of the current position trigger signal 412 both approximately occur at the time T 3 .
  • a pre-trigger lead time PTLT may be timed for the initiation of the current instance of the encoder position sample period 421 such that the average effective sample time 424 of the current instance of the encoder position sample period 421 is approximately the same as the actual timing of the current position trigger signal 412 at the time T 3 .
  • the pre-trigger signal 411 is generated at the time T 1 which occurs at the pre-trigger lead time PTLT before the actual timing of the current position trigger signal 412 that occurs at the time T 3 .
  • the pre-trigger lead time PTLT is determined (e.g., by the encoder position timing subsystem) and is a fraction of the duration of the defined encoder position sample period 421 during which the position encoder performs operations to acquire encoder position data associated with a current encoder position (e.g., the position of the transducer element 115 relative to the scale 112 of FIG. 1 ).
  • the pre-trigger lead time PTLT is approximately equal to one-half of the effective sample period 423 plus the transmitter setup period 422 of the encoder position sample period 421 .
  • the fine position calculation period 431 begins at the time T 5 and ends at a time T 6 .
  • the fine position calculation period 431 corresponds to a calculation of a fine position (e.g., in accordance with a position of the transducer element 115 relative to a fine scale track of the scale 112 of FIG. 1 ).
  • the serial response timeline 440 after the fine position calculation period 431 ends, the data transmission period 442 begins at the time T 6 and ends at a time T 8 .
  • the position encoder is operated to output the current instance of the encoder position data at a time associated with the current position trigger signal 412 , such that the host motion control system associates the current instance of the encoder position data with the current position trigger signal 412 .
  • the position encoder may be further operated to sample one of the coarser scale tracks of the scale 112 (e.g., scale track B or C), for which the position data from the coarser scale track is used to update the coarser portion of the absolute position in the following sample period.
  • the sampling of the scale track B or C may be alternated for subsequent sample periods, as will be described in more detail below.
  • the encoder position sample period 451 begins at the time T 5 and ends at a time T 9 . Similar to the encoder sample period 421 , the encoder position sample period 451 includes a transmitter setup period 452 from the time T 5 to a time T 7 , and an effective sample period 453 from the time T 7 to a time T 9 .
  • the encoder position sample period 451 corresponds to a sampling of a coarser scale track B (e.g., of the scale 112 of FIG. 1 ).
  • the coarse position update period 471 begins at the time T 9 and ends at a time T 10 .
  • the coarse position update period 471 corresponds to a calculation and update of a coarse position, in accordance with the sampling of the scale track B in the preceding encoder position sample period 451 .
  • the updated coarse position data is subsequently combined with fine position data from a subsequent fine position calculation period 432 , to determine an absolute position (e.g., of the transducer element 115 relative to the scale 112 of FIG. 1 ).
  • the encoder position sample period 425 begins at the time T 9 and ends at a time T 12 . Similar to the encoder position sample period 421 , the encoder position sample period 425 includes a transmitter setup period 426 from the time T 9 to a time T 10 , and an effective sample period 427 from the time T 10 to a time T 12 .
  • the effective sample period 427 has an average effective sample time 428 that corresponds to a time T 11 , which coincides with the actual timing of the current position trigger signal 414 within an allowed tolerance window ATW.
  • the fine position calculation period 432 begins at the time T 12 and ends at the time T 13 , which, similar to the fine position calculation period 431 , corresponds to a calculation of a fine position (e.g., in accordance with a position of the transducer element 115 relative to a fine scale track of the scale 112 of FIG. 1 ).
  • the updated coarse position data from the coarse position update period 471 is combined with the calculated fine position data from the fine position calculation period 432 in order to update the overall absolute position (e.g., of the transducer element 115 relative to the scale 112 of FIG. 1 ).
  • a data transmission period 445 begins at the time T 13 and ends at a time T 15 . Similar to the data transmission period 442 , the data transmission period 445 corresponds to operating the position encoder to output the current instance of the encoder position data (e.g., as calculated during the position calculation period 432 ) at a time associated with the current position trigger signal 414 , such that the host motion control system associates the current instance of the encoder position data with the current position trigger signal 414 . As illustrated in the sample scale C timeline 460 , the encoder position sample period 461 begins at the time T 12 and ends at the time T 16 .
  • the encoder position sample period 461 includes a transmitter setup period 462 from the time T 12 to a time T 14 , and an effective sample period 463 from the time T 14 to a time T 16 .
  • the encoder position sample period 461 corresponds to a sampling of the coarser scale track C (e.g., of the scale 112 of FIG. 1 ).
  • the sequence of FIG. 4 illustrates how the coarser scale tracks B and C (e.g., of an absolute encoder embodiment of the scale 112 of FIG. 1 ) are sampled in an alternating manner, as is performed during the data transmission periods 442 and 445 while the position data is being transmitted to the host motion control system.
  • the coarse position update period 472 begins at a time T 16 and ends at a time T 17 (e.g., corresponding to the calculation of the coarse position according to the sampling of the scale track C during the encoder position sample period 461 ). Similar to the coarse position update period 471 , the coarse position data determined during the coarse position update period 472 is utilized to update the coarser portion of the absolute position in the next position calculation period.
  • FIG. 4 illustrates how a pre-trigger signal may be utilized to reduce the overall response time that occurs between when a position trigger signal is sent from a host motion control system and when, in response, the transmission of position data back to the host motion control system begins.
  • the disclosed pre-trigger principles may be used for the sampling and position data determination of any one scale, or all scales of a position encoder, in various embodiments.
  • a system has a requirement that the response time (e.g., for the start of the transmission data) be within a required response time (e.g., within 10 microseconds of the receipt of the position trigger signal), and if the overall encoder position sample period (e.g., 16 microseconds) plus the position calculation period (e.g., 1 microsecond) takes longer than the required response time, it will be appreciated that if the sampling was not started until after the position trigger signal was received, the system would not be able to start transmitting the position data within the required response time.
  • a required response time e.g., within 10 microseconds of the receipt of the position trigger signal
  • the resulting overall response time for the start of the transmission of the position data may be less than the required response time (e.g., 10 microseconds).
  • FIG. 5 is a timing diagram 500 illustrating timelines 510 - 530 and signals 540 - 580 in a position encoder system in accordance with a second exemplary implementation.
  • an NC request timeline 510 illustrates position request periods 511 and 512 (e.g., including position trigger signals received from a host motion control system).
  • An NC response timeline 520 illustrates data transmission periods 521 and 522 .
  • each of the data transmission periods 521 and 522 correspond to the position encoder outputting a current instance of the encoder position data (e.g., as calculated, updated, etc.) at a time that is associated with a corresponding current position trigger signal that was previously received from the host motion control system.
  • a scale sample timeline 530 illustrates sample scale markers 531 - 534 , which correspond to respective scale sampling (e.g., of scale tracks A, B, or C).
  • An enable driver signal 540 includes signal portions 541 - 544 (e.g., for driving the transmitter coils 356 A- 356 C of the transducer element 315 of FIG. 3 ).
  • An enable analog-to-digital converter (ADC) signal 550 includes signal portions 551 - 554 (e.g., for enabling the ADC's 364 A- 364 C of the transducer electronic 316 of FIG. 3 ).
  • a drive waveform signal 560 includes signal portions 561 - 564 (e.g., corresponding to the schematically illustrated oscillating drive waveform for driving the transmitter coils 356 A- 356 C of the inductive transducer element 315 of FIG. 3 ).
  • the sample and hold filtered signal 570 includes signal portions 571 - 574 (e.g., corresponding to sample and hold values of the receiver coils 351 A- 351 C of the transducer element 315 of FIG. 3 ).
  • the ADC filtered output signal 580 includes schematically represented ADC signal conversion portions 581 - 584 (e.g., corresponding to the ADC values of the encoder position data as sampled from the respective scale tracks A, B or C). More specific details regarding the timing of the various signals illustrated in FIG. 5 will be described in more detail below.
  • a pre-trigger signal is generated (e.g., as provided by an encoder position timing subsystem), which initiates a sampling of a fine scale track A (e.g., similar to the encoder position sample period 421 of FIG. 4 for sampling the fine scale track A).
  • the enable driver signal 540 and the enable ADC signal 550 both transition from low to high at the time T 1 .
  • the drive waveform signal 560 begins oscillating and the sample and hold filtered signal 570 begins transitioning to a higher state approximately corresponding to the peaks of the drive waveform signal 560 , and the ADC filtered output signal 580 begins a period of stepped transitions.
  • a time T 2 (e.g., corresponding to a “driver start-up” timing) the peaks of the oscillating drive waveform signal 560 are shown to approximately reach a maximum state.
  • a position request period 511 begins as illustrated in the NC request timeline 510 , as may correspond to the receipt of a position trigger signal from the host motion control system.
  • a sample scale marker 531 is indicated as shown in the scale sample timeline 530 .
  • the enable driver signal 540 transitions from high to low, and the drive waveform signal 560 correspondingly ceases to oscillate and returns to a zero level.
  • the signal portion 541 (from the time T 1 to the time T 4 ) of the enable driver signal 540 and the corresponding signal portion 561 (from the time T 1 to the time T 4 ) of the drive waveform signal 560 are noted to correspond to the sampling of the fine scale track A.
  • the position request period 511 ends, as illustrated in the NC request timeline 510 .
  • the data transmission period 521 begins, as illustrated in the NC response timeline 520 .
  • T 7 e.g., corresponding to an “ADC ready” timing
  • the ADC is indicated as being ready (e.g., for the subsequent processes including the sending of the position data).
  • the process for sending/transmitting the position data begins, the enable ADC signal 550 transitions from high to low, and the sample and hold filtered signal 570 correspondingly begins a transition downward toward a zero level.
  • the ADC filtered output signal 580 begins a transition downward toward a zero level.
  • the signal portion 551 (from the time T 1 to the time T 8 ) of the enable ADC signal 550 , the signal portion 571 (from the time T 1 to the time T 8 ) of the sample and hold filtered signal 570 and the signal conversion portion 581 (from the time T 1 to the time T 9 ) of the ADC filtered output signal 580 are noted to correspond to the sampling of the fine scale track A.
  • the sampling process repeats for the sampling of the coarser scale track B (e.g., similar to the encoder position sample period 451 of FIG. 4 for sampling scale track B). It is noted that the sampling of the coarser scale track B is performed at least in part while the position data is being transmitted to the host motion control system (i.e., during the data transmission period 521 ), similar to the process of FIG. 4 .
  • the enable driver signal 540 and the enable ADC signal 550 both transition from low to high, and the drive waveform signal 560 correspondingly begins to oscillate, the sample and hold filtered signal 570 begins transitioning to a higher state (i.e., approximately following the peaks of the drive waveform signal 560 ) and the ADC filtered output signal 580 begins a period of stepped transitions, all as corresponding to the sampling of the coarser scale track B.
  • the enable driver signal 540 transitions from high to low, and the drive waveform signal 560 correspondingly ceases to oscillate and returns to a zero level.
  • the signal portion 542 (from the time T 10 to the time T 11 ) of the enable driver signal 540 and the signal portion 562 (from the time T 10 to the time T 11 ) of the drive waveform signal 560 are noted to correspond to the sampling of the coarser scale track B.
  • the data transmission period 521 ends, as illustrated in the NC response timeline 520 .
  • the enable ADC signal 550 transitions from high to low, and the sample and hold filtered signal 570 correspondingly begins transitioning downward toward a zero level, followed by the ADC filtered output signal 580 transitioning downward toward a zero level.
  • the signal portion 552 (from time T 10 to time T 13 ) of the enable ADC signal 550 , the signal portion 572 (from the time T 10 to the time T 13 ) of the sample and hold filtered signal 570 , and the signal portion 582 (from the time T 10 to the time T 13 ) of the ADC filtered output signal 580 , are noted to correspond to the sampling of the coarser scale track B.
  • a time T 14 e.g., corresponding to a “reset complete” timing
  • the sample and hold filtered signal 570 and the ADC filtered output signal 580 have completed transitioning to a zero level, for which the reset process is complete.
  • a second pre-trigger signal is generated (e.g., by the encoder position timing subsystem) at a time T 15 (e.g., corresponding to a “predictive start scale A” timing, similar to the time T 1 ), which starts the process for sampling the fine scale track A.
  • the signal portions corresponding to the sampling of the fine scale track A include the signal portion 543 of the enable driver signal 540 , the corresponding signal portion 563 of the drive waveform signal 560 , the signal portion 553 of the enable ADC signal 550 , and the corresponding signal portions 573 and 583 of the sample and hold filtered signal 570 and the ADC filtered output signal 580 , respectively.
  • a position request period 512 occurs (e.g., including a position trigger signal received from the host motion control system), and a corresponding sample scale marker 533 occurs in the scale sample timeline 530 .
  • a data transmission period 522 occurs as illustrated in the NC response timeline 520 (e.g., for transmitting to the host motion control system the position data corresponding to the sampling of the fine scale track A, as well as the updated coarse position data as determined from the previous sampling of the coarser scale track B during the times T 10 -T 14 ).
  • a sampling of the coarser scale track C begins at a time T 16 (e.g., corresponding to a “start scale C” timing, similar to the process at the time T 10 except with respect to the scale track C rather than the scale track B).
  • the signal portions corresponding to the sampling of the coarser scale track C include the signal portion 544 of the enable driver signal 540 , the corresponding signal portion 564 of the drive waveform signal 560 , the corresponding sample scale marker 534 in the scale sample timeline 530 , the signal portion 554 of the enable ADC signal 550 , and the corresponding signal portions 574 and 584 of the sample and hold filtered signal 570 and the ADC filtered output signal 580 , respectively.
  • the sample and hold filtered signal 570 and the ADC filtered output signal 580 have completed transitioning to a zero level, for which the reset process is complete.
  • the position data determined during the sampling of the coarser scale track C between the times T 16 and T 17 is utilized to update the coarser position portion of the absolute position in a following sequence of the sampling process (e.g., similar to the utilization of the coarse position data from the coarse position update period 471 in combination with the fine position data from the subsequent position calculation period 432 to determine the current overall absolute position data that is transmitted as part of the data transmission period 445 of FIG. 4 ).
  • FIG. 6 is a flow diagram illustrating one exemplary implementation of a routine 600 for operating a position encoder system including a position encoder that is configured to be utilized for outputting encoder position data corresponding to encoder positions and an encoder position timing subsystem.
  • a routine 600 for operating a position encoder system including a position encoder that is configured to be utilized for outputting encoder position data corresponding to encoder positions and an encoder position timing subsystem.
  • predictable times are determined when position trigger signals are expected to be received from a host motion control system.
  • the position trigger signals from a host motion control system may occur at predetermined time intervals (e.g., according to a known frequency).
  • the timing for subsequent position trigger signals may correspondingly be determined once a first position trigger signal is received (i.e., wherein the timing of the first position trigger signal is utilized as a basis for estimating the timing of the subsequent position trigger signals according to the known predetermined time interval between the position trigger signals).
  • the determining of the predictable times when the position trigger signals are expected to be received from the host motion control system may include inputting at least two consecutive position trigger signals to the encoder position timing subsystem, and determining a corresponding timing of the position trigger signals as indicated by a time difference between the at least two consecutive position trigger signals.
  • the determining of the predictable times may include inputting the repeated position trigger signals to the encoder position timing subsystem at the trigger frequency and determining a timing of the repeated position trigger signals.
  • the operating of the encoder position timing subsystem to initiate a current instance of the encoder position sample period at the pre-trigger lead time before the next predictable time of the position trigger signal may include initiating the current instance of the encoder position sample period at a time that corresponds to the pre-trigger lead time before the next predictable time of the position trigger signal.
  • the process for determining the predictable times may be repeated at later times (e.g., the measuring of the time differences between position trigger signals may be an ongoing process), so that any changes in the timing may be detected and so that the sample timing may be corrected and/or otherwise adjusted on an ongoing basis.
  • a pre-trigger lead time is determined that is a fraction of the duration of a defined encoder position sample period during which the position encoder performs operations to acquire encoder position data associated with a current encoder position.
  • the encoder position timing subsystem is operated to initiate a current instance of the encoder position sample period at the pre-trigger lead time before a next predictable time of the position trigger signal.
  • the encoder position sample period may correspond to a sampling of at least one fine track, wherein after the at least one fine track is sampled during the current instance of the encoder sample period, a second encoder sample period may be initiated at a later time for sampling the at least one coarse track before the next position trigger signal is received from the host motion control system.
  • an associated current instance of the encoder position data is determined as corresponding to the current instance of the encoder position sample period.
  • a current position trigger signal is received from the host motion control system, wherein the average effective sample time of the current instance of the encoder position sample period coincides with the actual timing of the current position trigger signal within an allowed tolerance window.
  • the position encoder is operated to output the current instance of the encoder position data at a time associated with the current position trigger signal, such that the host motion control system associates the current instance of the encoder position data with the current position trigger signal.
  • various corrective actions may be taken. For example, if the frequency of the position trigger signals has not changed (e.g., as determined by measuring the timing between position trigger signals), the timing of when the future position trigger signals are expected to be received may be shifted according to utilizing the timing of a most recently received position trigger signal as a basis for estimating when future position trigger signals will be received according to the known frequency. If the frequency of the position trigger signals is determined to have changed, the newly determined frequency may be utilized for estimating when future position trigger signals will be received. In some instances, a warning or other notification may be provided to a user with respect to position trigger signals that are not being received at expected times (e.g., so that corrective action can be taken, etc.).
  • various additional corrective actions may be taken. For example, with respect to a position calculation period and a position data transmission period that follow an encoder position sample period, such processes may be cancelled and/or otherwise modified based on a position trigger signal not having been received within an expected timeframe. More specifically, if a position trigger signal is not received by the time an encoder position sample period is complete, the processes for transmitting position data (e.g., as would otherwise be done in response to the receipt of a position trigger signal) may be cancelled, delayed, or otherwise modified.

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